The present invention relates to an optical device, more specifically to an optical device which can switch optical paths and deflect light.
Optical switches function as relay points for switching paths of light in an optical communication network and is an essential member of optical communication networks.
Recently, an optical switch which changes over paths of light by means of electro-optic effect (EO effect) has been proposed.
The proposed optical switch applies electric fields to an optical waveguide layer to control refractive indexes by the electro-optic effect, and can perform high-speed switching. The proposed optical switch requires no large current, and can drastically reduce electric power consumption in comparison with the thermo-optical switches. The proposed optical switch has no mechanically operative part, which makes the proposed optical switch highly reliable.
The proposed optical switch includes a number of prism electrodes in the deflecting unit. In the proposed optical switch, suitable voltages are applied to the respective prism electrodes to thereby deflect optical signals to required directions to lead the optical signals to desired channels.
As means for applying voltages to the respective prisms, it can be proposed, for example, to connect wires to the prisms electrodes by bonding. FIGS. 9A and 9B are diagrammatic views of the application of voltages to the prism electrodes through the wires connected to the prism electrodes by bonding.
As shown in FIGS. 9A and 9B, a slab waveguide layer 140 is formed on an optical waveguide substrate 112. A number of prism electrodes 118 are formed on the slab optical waveguide layer 140. Wires 102 are connected to the respective prism electrodes 118 by bonding. In the optical switch shown in FIGS. 9A and 9B, voltages are applied to the respective prism electrodes 118 through the respective wires 102.
However, the application of voltages to the prism electrodes 118 through the wires 102 connected by bonding makes the leading of the wires 102 very complicated.
Here, it is possible that an optical waveguide substrate with vias buried in is mounted on a control substrate, and voltages are applied to the prism electrodes from the control substrate via solder bumps and the vias. However, in this case, there is a risk that in the processing of joining the optical waveguide substrate and the control substrate, large shearing stresses may be applied to the solder bumps. That is, in a case where the optical waveguide substrate is formed of, e.g., ceramics, and the control substrate is formed of, e.g., a resin, the thermal expansion coefficient of the optical waveguide substrate and that of the control substrate are very different from each other. Due to the thermal expansion coefficient difference between the optical waveguide substrate and the control substrate, large shearing stresses are applied to the solder bumps, which consequently leads to lower reliability.